1. Field of the Invention
The present invention relates generally to an antenna device of a mobile terminal, and more particularly, to a whip antenna structure of a mobile terminal having a non-conducting projection at the lower end of the whip antenna.
2. Description of the Related Art
Generally, mobile terminals have an antenna device for data communication, which includes a helical antenna and a whip antenna.
An example of this type of the mobile terminal is shown in U.S. Pat. No. 5,204,678, in which the helical antenna is incorporated with the upper portion of the whip antenna. In this patent, the mobile terminal further includes a conducting projection electrically connected to the whip antenna, and an antenna bushing for fixing a receiving means and the antenna to the terminal. When retracting the whip antenna, the helical antenna descends in the retracting direction of the whip antenna so that a connector electrically connected to the helical antenna is electrically connected to a spring clip provided in the antenna bushing. Here, only the helical antenna operates since the whip antenna is electrically isolated from the helical antenna.
In another type of the mobile terminal, the helical antenna is mounted to the main body of the mobile terminal. An example of this mobile terminal is disclosed in U.S. Pat. No. 5,479,178, in which the whip antenna includes a conducting projection electrically connected to a conducting wire, and an antenna bushing for fixing a receiving means and the antenna to the mobile terminal. When the whip antenna is retracted, only the helical antenna is used; and otherwise when the whip antenna is extended, the projection is brought in contact with the spring clip to allow the whip antenna to be operated.
FIG. 1 is a cross section of a mobile terminal having an antenna with a conducting projection according to prior art.
Referring to FIG. 1, when extending a whip antenna 110, the conducting projection 119 is associated with a spring clip (not shown) provided in a bushing 120 so as to secure the whip antenna. However, there is a problem that the whip antenna cannot be extended when the spring force is stronger than a driving force of the antenna. Particularly, when using a small-sized driving motor 130 in order to miniaturize the mobile terminal, a force for extending the whip antenna 110 is too weak to allow the conducting projection 119 to be associated with the spring clip.
Further, the antenna having the driving motor 130 uses a power transmission device such as rollers 131 to impart an up-and-down motion to the whip antenna 110 to be extended/retracted. Here, the rollers 131 are positioned at the lower end of the bushing 120 for fixing the whip antenna. As illustrated in FIG. 1, the force transmitted from the motor 130 makes the rollers 131 rotate, thereby extending the whip antenna 110 between the rollers 131. As described previously, the conducting projection 119 is positioned lower than the bushing 120 due to the position of the rollers 131 such that the whip antenna is not entirely extracted from the mobile terminal and the conducting projection 119 is left in the mobile terminal. As a result, radiation and matching characteristics of the whip antenna are deteriorated. That is, in a general automotive antenna having a lower portion which includes a conductive stopper and an intermediate portion which has a different diameter for stopping extension of the antenna the whip antenna portion of the automatic antenna suffers deterioration of its radiation and matching characteristics.